• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Investigating Wires

Extracts from this document...

Introduction

‘Investigating wires’

       (D, DCP and CE)

Determining how the length of a nichrome wire changes the resistance

Introduction:

Electrical resistance is a ratio of the degree to which an object opposes an electric current through it. It can also be defined as the ratio of voltage per unit current through it, R=V/I. The unit of electrical resistance is the ohm (Ω). Resistance can be found using the two following formulas.

Resistance= (Potential Difference ÷ Current) ---> (which is more known as Ohm’s law) where the potential difference is measured in Volts (V) and the current can be measured in Amps (A). Another way the resistance can be found is by using the formula R= (image00.pngL)/ A. This is where the resistance (R) is related to: cross- sectional area (A), length (L) and material of the wire as R  L/A. The constant of proportionality is called the resistivity (image00.png).

So R= (image00.pngL)/ A

So for our theory work for this experiment, we know that R  L/A. Therefore let’s say that by assuming the wire follows Ohm's Law, the resistance of a wire is directly proportional to its length therefore doubling the length will double the resistance of the wire.

...read more.

Middle

1 Voltmeter 20/ 20 V ± 0.01 V2 crocodile clipsStopwatchMeter rule6 Connecting wires1 variable resistorNichrome wire- 220 cm altogether

[10cm, 20 cm, 30 cm, 40 cm, 50 cm and 60 cm(Note*- each length was used once)]

Method-

  1. Start of by cutting out six different lengths of nichrome wires of the same brand and thickness (10cm, 20 cm, 30 cm, 40 cm, 50 cm and 60 cm respectively) from a reel using a meter ruler. Do Note*- Three wires of each length were cut out i.e. there were three wires of 10cm, three wires of 20 cm and so on.
  2. The ammeter, power pack and nichrome wire (about to be tested for resistance) are connected in series using connecting leads.. Basically refer to the diagram displayed below as the experiment set up is exactly similar to that.
  3. Connect the voltmeter in parallel to the circuit.
  4. Next, turn on the power pack which is adjusted to the voltage we are working with (note, as previously mentioned, the voltage is a controlled variable therefore it is kept constant). At the same time start the stopwatch and begin timing.
  5. When thirty seconds have gone by (as mentioned previously, we are working with 30 s time intervals), the readings of the ammeter and the voltmeter must right away be taken.
...read more.

Conclusion

ngth of wire, the average resistance needs to be calculated and this can be done by using the following formula:

Average =    sum of readings 
                    number of readings

Example 2- Length of wire-0.10m,

Average         =    0.39+0.39+0.39 Ω
                                          3

                =0.39 Ω

Table 2: The average resistance for different lengths of wires

Length (±0.0005 m)

Trial 1

Trial 2

Trial 3

Average Resistance(Ω)

Resistance(Ω)

Resistance(Ω)

Resistance(Ω)

0.10

0.39

0.38

0.39

0.39

0.20

0.84

0.84

0.83

0.84

0.30

1.24

1.22

1.22

1.23

0.40

1.76

1.73

1.70

1.73

0.50

2.13

2.15

2.14

2.14

0.60

2.60

2.49

2.54

2.54

The uncertainty for reading of the length of wire was ± 0.0005m. This is because the smallest graduation of readings on a meter rule is 0.001m. In an analogue system the smallest graduation is divided by two to find the uncertainty. The uncertainty for the voltage is ± 0.01 V and the uncertainty for current is ± 0.01 A.

To find the uncertainty for resistance the fractional uncertainty for voltage and current had to be added. The fractional uncertainty is obtained by:

Fractional uncertainty= absolute uncertainty 
                                actual value

Example 4- Trial 1, Length-0.1m

Fractional uncertainty of voltage= absolute uncertainty 
                                               actual value

                                                   =(0.1/0.97)

                                     =0.103 V

Fractional uncertainty of current= absolute uncertainty 
                                               actual value

                                         =(0.1/2.46)

                                         =0.041

Uncertainty for resistance=Fractional uncertainty of voltage+fractional uncertainty of current

                                 =(0.1/0.97)+(0.1/2.46)

                                         =0.144

The average uncertainty was found by the formula

Average uncertainty= Sum of uncertainties
                         Number of uncertainties

Example 4- Length of wire-0.1m

Average uncertainty= (0.0146+0.0149+0.0148) Ω
                                             3

                          =0.0147 Ω

Determining the relationship between the length of wire and the resistance:

...read more.

This student written piece of work is one of many that can be found in our International Baccalaureate Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Physics essays

  1. Period of a loaded Cantilever (D, DCP, CE)

    When the equation is rearranged, it suggests a positive linear relationship between T2 and m with a gradient of , which does not support the results of this experiment. The main uncertainty in this experiment is damping. Evaluation Systematic uncertainties Damping is one of the main uncertainties in this experiment.

  2. An experiment to find the Resistivity of Pencil leads in different degree of hardness

    The gradient of the graph is also the resistance of the pencil lead. Hence the finding of R, the calculated gradient or resistance will then be used along with the cross-sectional area and the length of the pencil lead the resistivity formula.

  1. Resistance Lab. Aim - To investigate the effective resistance (total resistance) of ...

    (1 + 0.9 + 0.8 + 0.9)/4 = 0.9 (1.2 + 1.4 + 1.3 + 1.2)/4 = 1.275 Average value of V3 (volts) (3.7 + 3.5 + 3.9 + 3.6)/4 = 3.675 (5 + 5.1 + 4.8 + 5.1)/4 = 5 Value of R1 (ohms)

  2. Physics IA CE - Investigating the resistance of a wire

    Voltage - V/V �0.02 Current - I/A �0.10 Thickness - d/mm �0.01 Trial 1 (t1) Trial 2 (t2) Trial 3 (t3) Trial Avg (tavg) Trial 1 (t1) Trial 2 (t2) Trial 3 (t3) Trial Avg (tavg) 0.15 0.54 0.53 0.52 0.53 0.69 0.66 0.66 0.67 0.20 0.45 0.47 0.45 0.46

  1. In this extended essay, I will be investigating projectile motion via studying the movement ...

    Also, the range of the metal ball should be directly proportional to the compressed spring length. Thus, by doubling the compressed spring length, it would as double of the range of metal ball. Let's determine whether the hypothesis above applies to the experimental data.

  2. RESISTIVITY OF A MATERIAL

    resistance, just put the values of Voltage and Current into the formula. The way to calculate the area of wires' cross section is ?()2. Table 3: Length (m) Diameter (mm)�0.01mm Current (A)�0.01A Voltage (V)�0.01V Resistivity (?)�0.01? Area(,3.m.f) � 2.5 0.26 1.98 1.84 0.93 2.65 0.28 1.93 2.26 1.17 3.08 0.61

  1. How does the sinkage depth of a tyre affect its rolling resistance ?

    Arriving at the final conclusion for the rolling resistance based on the sole evidence of the sinkage depth on behalf of the air pressure of the tire. We can state that in order to determine the best possible value for the least resistance we would have to arrive at the

  2. HL Physics Revision Notes

    Coherent Waves - have a constant phase relationship. Laser light is coherent, a light bulb is not Monochromatic Waves - single frequency (wavelength). Contains only a very, very narrow band of frequencies Laser light is monochromatic, a light bulb is not Outline the mechanism for the production of laser light.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work